Vehicles may be fitted with evaporative emission control systems (EVAP) to reduce the release of fuel vapors to the atmosphere. For example, a fuel vapor canister packed with an adsorbent may adsorb and store refueling, running loss, and diurnal fuel vapors. At a later time, when the engine is in operation, the evaporative emission control system allows the vapors to be purged into the engine intake manifold for use as fuel. In an effort to meet stringent federal emissions regulations, emission control systems may need to be intermittently diagnosed for the presence of undesired evaporative emissions (leaks) that could release fuel vapors to the atmosphere. The data generated during each diagnostics test may be used to understand the results of the test, and the overall health of the EVAP system.
Accordingly, various approaches have been developed for transferring on-board diagnostics (OBD) data to an off-board location. One example approach, shown by Wang et. al. in US 20130246135 involves transferring diagnostic data from on-board diagnostics tests to a remote server. The vehicle's OBD unit may transfer the OBD data to the vehicle's electronic control units which may then transfer the data to a remote server either directly or via a smart device having a wireless communication module. The data may be analyzed at the remote location, and a signal may be sent to the vehicle operator to notify if there is a requirement for servicing one or more vehicle components.
However, the inventors herein have recognized potential issues with such a system. As one example, on-board diagnostics (OBD) of EVAP and other vehicle systems may generate a large quantity of data which may be difficult to efficiently transfer via available wireless communication. Also, a remote location with a sufficient data storage capacity (e.g., memory) may be required for storing all the available OBD data. As such, a part of the OBD data such as the start and the end points of a test may be transferred and stored at a remote location. However, the start and end points of the OBD data, such as EVAP system leak test data, may be influenced by vehicle operating conditions such as a hill climb or rough roads which may cause fuel sloshing. For example, a fuel tank pressure profile analyzed for EVAP system diagnostics may incorrectly indicate a leak during a driving condition that caused fuel sloshing. The erroneous diagnostic result may affect vehicle operation, and in the absence of complete OBD data, it may be difficult to comprehend the cause of the EVAP system leak indication. Also, due to access to only a limited portion of the OBD data, the data may not be efficiently analyzed at an off-board location.
In one example, the issues described above may be addressed by a method for a vehicle including an engine, comprising: fitting a function to one or more segments of a diagnostic dataset for an engine component on-board the vehicle; and transferring parameters of the function, and not the one or more segments of the dataset, to an off-board location. In this way, by efficiently fitting a curve to the OBD data, a smaller amount of data comprising the curve fitting parameters, and vehicle operating conditions may be transferred to an off-board location for analysis, storage, and future use.
As an example, during a diagnostic test of the EVAP system, a vacuum may be applied to a sealed EVAP system and the bleed-up of the pressure may be monitored. If the rate of pressure bleed-up is higher than a threshold rate, or the EVAP system pressure, after a pre-defined duration of the test, is higher than a threshold pressure, it may be inferred that there is presence of a leak in the EVAP system. If such a leak is detected, a part of the OBD data collected during pressure bleed-up may be fitted with a curve. The nature of the expected curve for this data may be retrieved from the controller memory. If it is possible to fit the data with the expected curve and get a curve fit that has a higher than threshold coefficient of determination (R2), it may be inferred that the diagnostic test results are reliable. However, if the expected curve does not provide a higher than threshold fit, one or more other curves are iteratively tried until a curve fit with a higher than threshold R2 value is achieved. For example, polynomials of different order, exponential curves, Gaussian curves, etc., maybe used for the curve fit. The entire data may be fitted with one curve, or the data may be divided into sections, and each section may be fitted with a distinct curve. Once a reliable curve fit has been achieved, the coefficients of the curve(s) and the R2 value(s) may be transferred to an off-board location. Also, the start and end data points, and vehicle operating conditions during the test, such as temperature, altitude, vehicle speed, vehicle location (retrieved from a global positioning satellite, for example), fuel level, engine load, etc., may be transferred to the off-board location. At the off-board location, the entire dataset may be reconstructed using the curve fitting co-efficients, and further analyzed. The controller may receive instructions from the off-board location for updating EVAP system leak test results and engine operations based on the data analysis. Also, during vehicle servicing, a technician at a service station may retrieve the entire diagnostic dataset from the information available at the off-board location and service the vehicle accordingly.
In this way, by fitting a diagnostics test data with a best fitting curve and transferring the coefficients of the curve to an off-board location, it may be possible to access and analyze the entire diagnostics dataset at the off-board location, and at a service station. In case of erroneous test results caused by external conditions (such as fuel sloshing during an EVAP system leak test), by utilizing instructions received from an off-board location, the on-board results may be updated, and engine operation may be optimized. The technical effect of fitting a curve to data collected on-board the vehicle, and transferring only the coefficients of the fit, along with start and end points of the data to an off-board location, is that faster transfer of data to the off-board location may be accomplished using a smaller band-width. Also, due to the transfer of a smaller, but more relevant, portion of the data, a smaller amount of storage space (memory) may be occupied at the off-board location. Overall, by fitting a curve, transferring a smaller amount of data, and curve fitting engine operating parameters, a larger portion of the OBD dataset (e.g., the entire portion) may be reproduced, and analyzed at the off-board location, thereby improving off-board processing of data. By increasing the accuracy and reliability of data processing without increasing storage or processor requirements, vehicle performance is improved.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.